A continuous molten plating process, which is a known technique for continuously plating a steel plate, uses rolls such as a sink roll and a support roll, which are located in a molten metal bath, to continuously guide a steel plate into the molten metal bath so that the steel plate passes through the molten metal bath. A thermal spray coating may be formed on the surface of a roll used in the molten metal bath for the purpose of improving the durability of the roll. For example, patent document 1 describes a thermal spray coating used for such a purpose that may be formed by thermally spraying powder obtained by calcining a mixture that contains tungsten carbide particles, tungsten boride particles, and cobalt particles.